Assuming the number you're looking for always starts with 0x and this sequence doesn't show up anywhere else in the code, use this:

my $data = join '', <DATA>;
if($data =~ /(0x\w+)/) {
    print "$1\n";
}

__DATA__
1:05:02.599,xx:MTV = 0x2f7c:COOL_CALL, an option = 11
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Also assuming that the hex number is terminated by a non-word ([^a-zA-Z0-9_]) character.