I want to put the modifier string to a regular expression into a variable, so that the modifiers can be selected at runtime. However, my naive attempt does not work:

#!/usr/bin/perl -w

use strict;

my $opts = "io";
my $regex = "test";

my $file = "./testfile";
open(my $fd, '<', "$file") or die "$!";
my @ary = <$fd>;
close $fd;
for my $line (@ary) {
        print $line if ($line =~ /$regex/$opts);
}

> ./test.pl test.txt 
Scalar found where operator expected at ./test.pl line 13, near "/$reg
+ex/$opts"
    (Missing operator before $opts?)
syntax error at ./test.pl line 13, near "/$regex/$opts"
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...and I've tried wrapping the comparison in an eval block, but to no avail. Is making the regex modifiers ... modifiable possible?

Thanks in advance for any hints, slaps upside the head, etc.