perl - Regex find a substring in a string containing a pattern -

so if string $a = "blah bluh bu.du" check if string has du in using:

if( $a =~ /\.du+/) 

now confirmed string has ".du" in it. how can word budu saved new string $b? using perl sorry, du supposed file extension

surround part want capture in parenthesis.

if( $a =~ /([a-za-z]*?du[a-za-z]*?)/){     if ( defined $1 ) {         $word = $1;         print "$word\n";     } }