/[(.*?)]/ won't match anything having to do with square brackets. It is a character set (the  [] metacharacters) consisting of the  ( ) . * ? characters.

Update: Something like  m{ \[ ([^]]*) \] }xms might be useful:

>perl -wMstrict -le
"my $s = 'foo [bar baz] quux [%^&*] boff [] biff';
 my @bracketed = $s =~ m{ \[ ([^]]*) \] }xmsg;
 print qq{'$_'} for @bracketed;
 @bracketed = $s =~ m{ \[ [^]]* \] }xmsg;
 print qq{'$_'} for @bracketed;
"
'bar baz'
'%^&*'
''
'[bar baz]'
'[%^&*]'
'[]'
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