c:\@Work\Perl\monks>perl -wMstrict -le
"my %hash = ('$1' => 'oops',  'abc' => 'ok');
 ;;
 'abc' =~ m{ (abc) }xms;
 print qq{captured '$1'};
 ;;
 print $hash{'$1'};
"
captured 'abc'
oops
[download]

You missed the point. Imho RHS of s/// isn't evaluated w/o e flag.

Cheers Rolf

_{(addicted to the Perl Programming Language and ☆☆☆☆ :)}

13:25 >perl -wE "my %h = (x => 0, '$1' => 1); my $s = 'axb'; say $s =~
+ s/(x)/$h{$1}/r; say $s =~ s/(x)/$h{'$1'}/r;"
a0b
a1b

13:27 >
[download]

?

Athanasius <°(((>< contra mundum

Iustus alius egestas vitae, eros Piratica,

Hi AnomalousMonk, thanks for your reply. I probably should have specified that I'm pretty new to perl. Could you comment at all at what your code does?

The code example above was meant as a counter-example to what I understood LanX to be saying. Comments:

my %hash = ('$1' => 'oops',  'abc' => 'ok');  # create a hash

'abc' =~ m{ (abc) }xms;   # capture a sub-string to $1
print qq{captured '$1'};  # show what that string is

print $hash{'$1'};  # show effect of single-quotes: no interpolation
[download]

Had  $1 been used directly (as in $hash{ $1 }), the output would have been 'ok'. A more complete example:

c:\@Work\Perl\monks>perl -wMstrict -MData::Dump -le
"my %hash = ('$1' => 'oops',  'abc' => 'ok');
 dd \%hash;
 ;;
 'abc' =~ m{ (abc) }xms;
 print qq{captured '$1'};
 ;;
 print 'single-quoted: ', $hash{'$1'};
 print 'straight: ', $hash{ $1 };
"
{ "\$1" => "oops", "abc" => "ok" }

captured 'abc'
single-quoted: oops
straight: ok
[download]

---

Give a man a fish:   <%-(-(-(-<

It works with strings too :)

use 5.020;
use warnings;

my %h = ( foo => 1, bar => 2 );

$_ = 'foobar';
s/(foo)/$h{'$1'}/;
say $_;

$_ = 'foobar';
s/(foo)/$h{$1}/;
say $_;

my $foo = 'foo';
say "$h{'$foo'}bar";
[download]

Use of uninitialized value $h{"$1"} in substitution iterator at extr.p
+l line 7.
bar
1bar
Use of uninitialized value $h{"$foo"} in concatenation (.) or string a
+t extr.pl line 15.
bar
[download]

OK I understand now what's happening, thanks! :)

The interpolation is done by translating to a concat which is executed.

(parsing hell)

Cheers Rolf

_{(addicted to the Perl Programming Language and ☆☆☆☆ :)}

update

see update in this post for an explanation of how interpolation works.