Yeah, your regex is pretty bad, and in this simple case you don't even need a regex.

my @array;
my $match = 'some_criteria';

while (<FH>) {
    chomp;  # thanks gwadej for reminding me
    my ($x,$y) = split /\t/, $_;
    if ( $x eq $match ){   
                push @array, $y;
             }
}
 
print "@array\n";
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