"usually - you need 'm' for 'match' ..."

You don't need it for /pattern/ or 'pattern'. You also don't need it for ?pattern?; however, that construct is deprecated.

#!/usr/bin/env perl
use strict;
use warnings;
my $x = 'abc';
if ($x =~ /b/) { print "y\n" } else { print "n\n" }
if ($x =~ 'b') { print "y\n" } else { print "n\n" }
if ($x =~ ?b?) { print "y\n" } else { print "n\n" }
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Output:

$ junk
Use of ?PATTERN? without explicit operator is deprecated at ./junk lin
+e 7.
y
y
y
[download]

See perlop - Regexp Quote-Like Operators for details.