Your error messages say what is wrong. The syntax @foo =~ m/$re/ does not do what you want it to.

You should look at each line separately and try the lookup with each. I'd be inclined to use the index builtin instead of regex matching, since you have the particular number you want to look for. Here's what I'd do, sticking close to what you wrote,

# after getting @number
my $wanted = '9432';
for (@number[0..99]) {
    if (index($_, $wanted) != -1) {
        print "match found\n";
    }
    else {
        print "match failed\n";
    }
}
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There are a couple of things there you may not have seen before. I used an array slice to limit the number of items searched, where you used a while loop. The other is the index function itself.