http://www.perlmonks.org?node_id=735432


in reply to Re^2: Bug in substitution operator?
in thread Bug in substitution operator?

update: my example went the wrong way. This is the issue:
use strict; my $v = 'x'; print qq"$v{a}"; __END__ xa
versus
use strict; my $v = 'x'; print qq{$v{a}}; __END__ Global symbol "%v" requires explicit package name at -e line 3.
I think the following quote from perlop under "Gory details of parsing quoted constructs" sheds some light on this quirk:

Note also that the interpolation code needs to make a decision on where the interpolated scalar ends. For instance, whether "a $b -> {c}" really means:
"a " . $b . " -> {c}";
or:
"a " . $b -> {c};
Most of the time, the longest possible text that does not include spaces between components and which contains matching braces or brackets. because the outcome may be determined by voting based on heuristic estimators, the result is not strictly predictable. Fortunately, itís usually correct for ambiguous cases.

I don't see this as a bug. Remember that the right-hand-side of s/// is just a double-quoted string, subject to the usual interpolation rules.

The same disambiguation is needed in regular interpolated strings. Consider this snippet:

use strict; my $var = "this"; print "$var{whatever}"; __END__ Global symbol "%var" requires explicit package name at -e line 3.
To fix the syntax error, and get the desired output, you do this:
use strict; my $var = "this"; print "${var}{whatever}"; __END__ this{whatever}