>perl -wMstrict -le
"$_ = '1:A silly sentence (495,a), silly but useful.(3)';
 ;;
 EXPRESSION: {
   print qq{\n};
   print 'Enter a regular expression:';
   my $expression = <STDIN>;
   last EXPRESSION unless $expression =~ m{ \S }xms;
   chomp($expression);
   print qq{Expression is '$expression'};
   ;;
   if (! defined($expression = eval qq{qr/$expression/})) {
     print qq{Regex error: $@};
     redo EXPRESSION;
     }
   ;;
   if ($_ !~ $expression) {
     print 'The expression does not match the string';
     redo EXPRESSION;
     }
   print 'The expression matches the string';
   ;;
   if ($#- < 1) {
     print qq{No capture groups};
     redo EXPRESSION;
     }
   ;;
   for my $cg (1 .. $#-) {
     printf qq{capture group \$$cg is '%s' starting at offset %d \n},
       substr($_, $-[$cg], $+[$cg]-$-[$cg]), $-[$cg];
     }
   redo EXPRESSION;
   }
 ;;
 print 'done';
"


Enter a regular expression:
foo
Expression is 'foo'
The expression does not match the string


Enter a regular expression:
\d{2,}
Expression is '\d{2,}'
The expression matches the string
No capture groups


Enter a regular expression:
(\d{2,})
Expression is '(\d{2,})'
The expression matches the string
capture group $1 is '495' starting at offset 20


Enter a regular expression:
(\w+).*(\1)
Expression is '(\w+).*(\1)'
The expression matches the string
capture group $1 is 'silly' starting at offset 4
capture group $2 is 'silly' starting at offset 28


Enter a regular expression:
(\w+).*(\d{2,}).*(\1)
Expression is '(\w+).*(\d{2,}).*(\1)'
The expression matches the string
capture group $1 is 'silly' starting at offset 4
capture group $2 is '95' starting at offset 21
capture group $3 is 'silly' starting at offset 28


Enter a regular expression:
\d***
Expression is '\d***'
Regex error: Nested quantifiers in regex; marked by <-- HERE 
in m/\d** <-- HERE */ at (eval 6) line 1, <STDIN> line 6.


Enter a regular expression:
silly
Expression is 'silly'
The expression matches the string
No capture groups


Enter a regular expression:

done