what's the regular expression to find two sets of parenthesis in a row using perl?

Question

I have rows with different sets of parenthesis. For example

     (sdfsfs) (sfdsfd) 
     (sdfsfs) (sfdsfd) (sfdsfd) 
     (sdfsfs) (sfdsfd) (sfdsfd) (sfdsfd)
            


        

Answer 1

^(?:\s*\([^\)(]*\)\s*){2}$

You can define this pattern with anchors.See demo.

https://regex101.com/r/eX9gK2/10

Answer 2

You can use this regex to match a line with exactly 2 parentheses sets:

m/^(\([^)]*\)\s*){2}$/

OR:

m/^\([^)]*\)\s*\([^)]*\)$/

RegEx Demo

[^)]* will match any character but ) and is more efficient than .*? or .*.

Answer 3

This is a better solution.

while ( $text =~ //(?m)^(?=(?:.*?(?&parens)){2})(?!(?:.*?(?&parens)){3}).+$(?(DEFINE)(?<parens>\([^)\n]*\)))/g )
{
    print $&,"\n";
}

Formatted:

 (?m)                          # Multi-line mode
 ^                             # BOL
 (?=                           # Must be 2 paren's blocks
      (?:
           .*? (?&parens) 
      ){2}
 )
 (?!                           # Cannot be 3 paren's blocks
      (?:
           .*? (?&parens) 
      ){3}
 )
 .+                            # Get the entire line
 $                             # EOL

 (?(DEFINE)
      (?<parens> \( [^)\n]* \) )    # (1)
 )