#!/usr/bin/perl -w
use strict;

sub find {
    local *IN = shift;
    my $find_me = shift;
    my $count   = 0;

    # duplicate existing file handle
    open F2, '<&', *IN or die "Can not duplicate file handle";
    my $tell = tell(F2);
    while (<F2>) {
        $count++ if (/$find_me/);
    }

    return "count: $count tell: $tell\n";
    close F2;
}

open OUT, '>', 'tmp.txt' or die "$!\n";
print OUT while (<DATA>);
close OUT or die "$!\n";

open IN, 'tmp.txt' or die "$!\n";

print find( *IN, 'a' );
print find( *IN, 'a' );
print find( *IN, 'd' );
print find( *IN, 'e' );

__DATA__
a
a
a
c
d
e