replace multiple locations of string with function call back

use strict;

my $text=<<'_end';
1 + 1
2+2
and
3+3
_end

print "before:\n$text\n";

$text =~ s/(\d+)\s*\+\s*(\d+)/&hello($&, $1, $2)/ge;

print "after:\n$text\n";


sub hello {
 my ($line, $n1, $n2)=@_;
 my $sum=$n1+$n2;
 return "$line=$sum";
}

before:
1 + 1
2+2
and
3+3

after:
1 + 1=2
2+2=4
and
3+3=6