Re: preserving hash value outside the loop

[hippo]

Yes, it is possible. Simply declare $key outside the while loop instead of inside it. See Coping with Scoping.

Of course you'll only see the value from the last time $key is set but it's not immediately clear from your post if that's a problem for you.

[Anonymous Monk]

yes I declared $key outside the loop but then this is also the problem that it gives the last value set to $key. Actually I want to print each value of $key and $key1 separated by tab.

[hippo]

So, why not prepend the key to the list in the first loop instead:

#!/usr/bin/env perl
use strict;
use warnings;

my %seen;

$/ = "";
while (<>) {
    chomp;
    my ($key, $value) = split ('\t', $_);

    my @lines = split /\n/, $key;
    my $key1 = $lines[1];

    $seen{$key1} //= [ $key ];
    push (@{$seen{$key1}}, $value);
}

foreach my $key1 (sort keys %seen) {
    print join ("\t", @{$seen{$key1}});
}

If this doesn't do it for you then perhaps you might state what grander problem it is that you are trying to solve and a better overall approach might be in order.