Question

Script:

$aString = "This is Just a temp string just for fun";

print '^^^^^^^^' . "\n";

if( $aString =~ /^This\sis.*just/ )
{
    print $aString . " ->true<-\n" . "^^^^^^^^" ."$1";
}
else
{
    print $aString . " ->false<-\n" . "^^^^^^^^" ."$1"
}

Output:

^^^^^^^^

This is Just a temp string just for fun ->true<-

^^^^^^^^

Questions:

1. Why $1 is empty?
2. How to know how much sub-expression in aString is matched?

Pls clarify.

Answer 1

Why $1 is empty?

Your expression has no capture groups (()) in it. Perhaps you mean:

$aString =~ /^This\sis(.*)just/

How to know how much sub-expression in aString is matched?

Once you have captured some data, you can test it however you like.