merlyn and broquaint beat me to it with much better solutions, but here is my effort for what its worth.

Regards,
Dom.

use strict;
use warnings;
use Data::Dumper;

my @numbers = ('25', '12', '32','56','45','21','65');
my @needed = ('25','32','45','65');

my ($iNeeded, %hashNeeded, $iNumber, @result);
my $bWithinMatch = 0;

foreach $iNeeded (@needed) { $hashNeeded{$iNeeded} = 1 }

foreach $iNumber (@numbers) {
    
    #Are we within a match?
    if ($bWithinMatch) {push @result, $iNumber}

    #Is this a needed number?
    if (defined $hashNeeded{$iNumber}) {
        
        #Change state
        $bWithinMatch = not $bWithinMatch;
        
        #If this is the start of a match, store the result
        if ($bWithinMatch) {push @result, $iNumber}
    }
        
}

print Dumper(\@result);
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