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while(my $pline=<PRFILE>) {
    chomp $pline;
...
    my @parfields = split();
    ...
}

CHILD: foreach (@carray) {
    # search <PRFILE> line-by-line for a match of $_ to field #5
    # if each field#5 in <PRFILE> is guaranteed unique, you can go to 
+the next CHILD element once a match is found
}

my %lookupHash = ();
while(my $line=<CHFILE>) {
...
    $lookupHash{ $fields[1] } = ();        # $field[1] = 2nd field
    #$lookupHash{ $fields[1] } = $line;    # need entire line?
}

while(my $line=<PRFILE>) {
    chomp $line;
    my @fields = split(/\|/, $line);
    print $OUTFILE $line."\n" if(exists $lookupHash{ $fields[4] });
}

field            pre  suf               $HoH{$pre}->{$suf} = ()
---------------- ---- ----------------- ------------------------
1400000042597061="1" +"400000042597061" $HoH{1}->{400000042597061}=();
                ="14"+"00000042597061"  $HoH{14}->{00000042597061}=();
                    ...

field            prefix       suffix   $HoH{$suf}->{$pre} = ();
---------------- -----------  -------- -------------------------
1400000042597061="1400000042"+"597061" $HoH{597061}->{1400000042}=();

my $prefix = substr($myField, 0, 11);
my $suffix = substr($myField, 11);

my %lookupHash = ();
LINE: while(my $line=<CHFILE>) {
...
    $lookupHash{$suffix}->{$prefix} = ();
    #$lookupHash{$suffix}->{$prefix} = $line;
}

LINE: while(my $line=<PRFILE>) {
    chomp $line;
...
    # ... or output the child line if you needed that one
    #print $OUTFILE $lookupHash{$suffix}->{$prefix}."\n";
}