I don't understand what you mean with that last sentence, do you really want to continue from the exact line the sub finished at? That menas you will have to read that line twice, once in the sub and once i the main routine, by pushing the line back into the buffer, or pass back that line to the main function using return values. Try to avoid that. I usually read a file in only one place and use some sort of state machine to control what I want to do with what I read.

Anyway, if this is just a question regarding filhandle referencies, see the perlref and perlreftut. Also, I made a small example on filehandle referencing:

#!/usr/bin/perl -w

open SESAME, "testfil";

while (<SESAME>) {
        chomp;
        print "main: $_ ";
        if ($_ =~ /baz/) { print "go! \n"; &aSub(*SESAME) }
        print "\n";
}

sub aSub {
        my $inFile = shift;
        while (<$inFile>) {
                chomp;
                print "sub: $_";
                if ($_ =~ /bao/ ) { print " return!"; return };
                print "\n";
        }
}
[download]

the testfile is simple:

foo
bar
baz
bam
bao
fee
fie
[download]