Thanks again. I think you have come up with the simplest way to do this, although I modified the code slightly (below - doesn't run but is a simplified example of what I was doing). Originally I was wondering if there was a built-in technique that I was missing, but it appears not.

Thanks again

#!/usr/bin/perl -ws

use strict;

open my $fh, '<', 'file.txt' or die $!;

my @lines = (
    "this is line 1; foo \n",
    "this is line 2: bar \n",
    "this is line 3: foobar \n",
);

print "PRINTING FROM FH\n";
working_routine($fh);

print "\n\nPRINTING FROM ARRAY\n";
working_routine(\@lines);


sub create_iter {
    my $arg = shift;
    if (ref $arg eq 'GLOB') {
        return <$arg>;
    }
    elsif (ref $arg eq 'ARRAY') {
        return shift @$arg;
    }
    else { die "Unknown type\n"}
}

sub working_routine{
    my ($data) = @_;
    my $flag = 0;
    while(my $line = create_iter($data)){
        if($line =~ /matches something/){
            next;
        }
        elsif($line =~ /matches something else/ and ! $flag){
            create_iter($data);
            my $newline = create_iter($data);
            dosomethingto($newline);
        }
        elsif($line =~ /gotcha/ && $flag){
            morework($line);
        }
        else{
            next;
        }
    }
}
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