or download this
$ perl -Mstrict -Mwarnings -le 'my $x = "-"; print $x =~ m-[ /\\-]- ?
+1 : 0'
Unmatched [ in regex; marked by <-- HERE in m/[ <-- HERE /\\/ at -e l
+ine 1.
...
$ perl -Mstrict -Mwarnings -le 'my $x = "-"; print $x =~ m![ /\\-]! ?
+1 : 0'
1