my %hash;
open my $TAB, "<", $tab_file or die "Cannot open $tabfile $!";
while (my $line = <$TAB>) {
    my $key = (split /\t/, $line)[0];
    $hash[$key] = $line;
}
close $TAB;

##</code><code>##

if (exists $hash{$xml_word}) {
    my $line = $hash{$xml_word};
    # now do what you want with $line
}