Variables & sigils

The match & error variables $/ and $!

Full

Two special variables Raku sets for you — the last regex match and the last error.

Two special lexical variables are populated automatically: $/ holds the most recent regex match, and $! holds the most recently caught exception. The capture shortcuts and error handling both read from them.

$/ — the match #

A successful ~~ against a regex sets $/. The positional captures $0, $1, … are shortcuts into it ($0 is $/[0]).

"abc123def" ~~ /(\d+)/;
say ~$/;
say ~$0;

Output

123
123

$! — the error #

Inside (or after) a failed try, $! holds the exception, whose .message is its text.

try { die "oops" }
say $!.message;

Output

oops

Notes #

$/ is why $0/$<name> work anywhere after a match — they don't need to be in the if that did the matching, just in the same scope.
Both are ordinary lexicals, so their value is scoped to the current routine/block; a nested match sets its own $/.
After a successful try, $! is reset to an undefined value, so $!.defined is a clean "did the last try fail?" test.