Regex search and replace match only

Question

In perl I have a long string but here is the important part $abc = "...Testvalue1 100...";

Is there a way to use Regex to search for the number right after Testvalue# and replace it with a variable?

Here is what I have so far:

my $abc = "...Testvalue1  100...";
for my $i (1..100) {
    $abc =~ s/Testvalue\d+\W+(\d+)/$i/;
    print $abc . "\n";
}

Unfortunately this replace the entire match with $i , not just the first match of (\\d+). Is there a way to do this?

My desired output would be:

Testvalue1  1
Testvalue1  2
...
Testvalue1  100

Answer 1

If you're using Perl 5.10 or newer:

$abc =~ s/ Testvalue \d+ \s+ \K \d+ /$i/x;

(mnemonic for \\K : "keep" everything to the left)

If you're not:

$abc =~ s/ ( Testvalue \d+ \s+ ) \d+ /$1$i/x;

(capturing the data you don't want to lose).

Answer 2

In Perl you can use:

$abc =~ s/Testvalue\d+\W+\K\d+/$i/;

\\K resets the starting point of the reported match. Any previously consumed characters are no longer included in the final match.