perl-如何找到模式的所有巧合

Question

For example I have a string "babdbeb" and pattern "bb". I want to find following substrings here:

bab
bdb
beb

What is the best way of doing this?

PS I'm very new to Perl programming.

Answer 1

You can use a lookahead pattern, see perlre

while ("babdbeb" =~ m/b(?=(.b))/g) {
        print "b$1\n";
}

This yields a match without the leading b , but allows to restart the search and find intermediate bb s

Answer 2

my $s = "babdbeb";
while ($s =~ /(b.b)/g) {
  print "$1\n";
  # decrease position where search left of by 2 (3 is length of 'b.b' -1)
  # pos() is lvalue function http://perldoc.perl.org/functions/pos.html
  pos($s) -= (length($1) -1);
}

output

bab
bdb
beb

Answer 3

You can use overlapping regex matching using positive lookahead assertion. Here is an example:

$\ = $/; ## adding \n after every print.

my $string = "babdbeb";
print for $string =~ /(?=(b.b))/g;

Output:

bab
bdb
beb