I have written the code using XML::Smart, as perl in my box is not an updated one. Also, I have tweaked the XML a little bit.

XML:

<OUTMOST>
        <MYENVDETAILS>
                <ENVDETAILS id="abc" >
                        <DMGRHOST>a.b.c.d</DMGRHOST>
                        <CELL>XYZ</CELL>
                        <NODEDETAIL nodeid="1" NODEHOST="v.x.y.z" >
                                <IHSNODE>v_ihsnode</IHSNODE>
                                <IHSJVM ihsjvmtype="log_ihs" >
                                        <IHSJVMNAME>abc_logihs1</IHSJV
+MNAME>
                                </IHSJVM>
                                <JVM jvmtype="api" >
                                        <JVMNAME>abc_api1.1</JVMNAME>
                                        <JVMNAME>abc_api1.2</JVMNAME>
                                </JVM>
                        </NODEDETAIL>
                </ENVDETAILS>
        </MYENVDETAILS>
</OUTMOST>
[download]

Execution

----- myaccount  v.x.y.z /appl/ -----
$ ./my_topologyParser.pl fetch
abc
----- myaccount  v.x.y.z /appl/ -----
$ ./my_topologyParser.pl nodesall
v.x.y.z
----- myaccount  v.x.y.z /appl/ -----
$ ./my_topologyParser.pl abc nodewrtseg
v.x.y.z
----- myaccount  v.x.y.z /appl/ -----
$ ./my_topologyParser.pl abc jvmtype api
abc_api1.1
abc_api1.2
----- myaccount  v.x.y.z /appl/ -----
$ ./my_topologyParser.pl abc jvmwrtnode v.x.y.z api
abc_api1.1
abc_api1.2
----- myaccount  v.x.y.z /appl/ -----
$ ./my_topologyParser.pl abc nodewrtjvm abc_api1.2
v.x.y.z
----- myaccount  v.x.y.z /appl/ -----
[download]

Actual Code

#!/appl/perl/bin/perl

use XML::Smart;
use strict;
use warnings;

$ENVFILE="/appl/test_MYENV_Top.xml";

my $ENVxml = XML::Smart->new($ENVFILE) || die ("Could not find file.")
+;

my $env = $ARGV[0];

if ( $ARGV[0] eq "fetch" ) {
        my @envname=$ENVxml->{OUTMOST}->{MYENVDETAILS}->{ENVDETAILS}('
+[@]','id');
        foreach my $i (@envname) {
                print "$i\n";
}
}
elsif ($ARGV[0] eq "nodesall"){
        my @envname=$ENVxml->{OUTMOST}->{MYENVDETAILS}->{ENVDETAILS}('
+[@]','id');
        foreach my $i (@envname) {
                my @nodename=$ENVxml->{OUTMOST}->{MYENVDETAILS}->{ENVD
+ETAILS}->('id','eq',"$i")->{NODEDETAIL}('[@]','NODEHOST');
                foreach my $c (@nodename) {
                        print "$c\n";
                }
        }
}
elsif ($ARGV[1] eq "nodewrtseg"){
        my @nodename=$ENVxml->{OUTMOST}->{MYENVDETAILS}->{ENVDETAILS}-
+>('id','eq',"$env")->{NODEDETAIL}('[@]','NODEHOST');
        foreach my $i (@nodename) {
                print "$i\n";
        }
}
elsif ($ARGV[1] eq "jvmtype") {
        my $typeCheck=$ARGV[2];
        my @jvmlist;
        my @nodename=$ENVxml->{OUTMOST}->{MYENVDETAILS}->{ENVDETAILS}-
+>('id','eq',"$env")->{NODEDETAIL}('[@]','NODEHOST');
        if ($#nodename < 0){
                exit 1;
        }
        foreach my $i (@nodename) {
                my @names=@{$ENVxml->{OUTMOST}->{MYENVDETAILS}->{ENVDE
+TAILS}->('id','eq',"$env")->{NODEDETAIL}->('NODEHOST','eq',"$i")->{JV
+M}->('jvmtype','eq',"$typeCheck")->{JVMNAME}};
                if ($#names > 0){
                        push(@jvmlist,@names);
                }
        }
        @jvmlist = grep /\S/, @jvmlist;
        if ($#jvmlist < 0){
                print " No $typeCheck type jvm found on $env . Incorre
+ct jvm type passed.\n";
        exit 1;
        }
        foreach my $c (@jvmlist) {
                print "$c\n";
        }
}
elsif ($ARGV[1] eq "jvmwrtnode") {
        my $nodeCheck=$ARGV[2];
        my $typeCheck=$ARGV[3];
        if (defined $nodeCheck && defined $typeCheck){
                my @names=@{$ENVxml->{OUTMOST}->{MYENVDETAILS}->{ENVDE
+TAILS}->('id','eq',"$env")->{NODEDETAIL}->('NODEHOST','eq',"$nodeChec
+k")->{JVM}->('jvmtype','eq',"$typeCheck")->{JVMNAME}};
                if ($#names < 0){
                        print " No $typeCheck type jvm found on $nodeC
+heck node. Incorrect type/nodename passed.\n";
                        exit 1;
                }
                @names = grep /\S/, @names;
                foreach my $c (@names) {
                        print "$c\n";
                }
        }
        else
        {
                print " No Node type or nodename passed. Incorrect no.
+ of arguments passed.\n";
                exit 1;
        }
}
elsif ($ARGV[1] eq "nodewrtjvm") {
        my $jvmCheck=$ARGV[2];
        if (defined $jvmCheck){
                my @nodename=$ENVxml->{OUTMOST}->{MYENVDETAILS}->{ENVD
+ETAILS}->('id','eq',"$env")->{NODEDETAIL}('[@]','NODEHOST');
                if ($#nodename < 0){
                        exit 1;
                }
               OUTER: foreach my $i (@nodename) {
                        my @jvmtypes=$ENVxml->{OUTMOST}->{MYENVDETAILS
+}->{ENVDETAILS}->('id','eq',"$env")->{NODEDETAIL}('NODEHOST','eq',"$i
+")->{JVM}('[@]','jvmtype');
                        foreach my $k (@jvmtypes) {
                                my @names = @{$ENVxml->{OUTMOST}->{MYE
+NVDETAILS}->{ENVDETAILS}->('id','eq',"$env")->{NODEDETAIL}->('NODEHOS
+T','eq',"$i")->{JVM}('jvmtype','eq',"$k")->{JVMNAME}};
                                if ($#names >= 0){
                                        foreach (@names){
                                         if ( $_ eq $jvmCheck ){
                                                print "$i\n";
                                                last OUTER;
                                                }
                                        }
                                }
                        }
                }
        }
}
else{
        print "\nThis parser is argument specific.";
        print "\n1). $0 fetch : To list out environments";
        print "\n2). $0 nodesall : To list all nodes of all environmen
+ts.";
        print "\n3). $0 <segID> nodewrtseg : to list all nodes of spec
+ific environment.";
        print "\n4). $0 <segID> jvmtype <typeofjvm> : to list all node
+s having specified jvmtypes of the specific environment.";
        print "\n5). $0 <segID> jvmwrtnode <nodename> <typeofjvm> : to
+ list all jvms present on specific node of specific type of the envir
+onment.";
        print "\n6). $0 <segID> nodewrtjvm <jvmname> : to list the nod
+e of specific jvm of specified environment.\n";
}
[download]

I know I could have used getopts, however, I was in a hurry :)