I'm completely mystified by this.

In the 3 example code blocks below I'm pushing the same things onto an array.

When I push the result of a failed match, nothing is pushed onto the array (unless I first save the result in a variable).

Why is this?!

Thanks!

use strict;
use warnings;


my @foo;
push @foo, 1;                   print scalar @foo, "\n";      # output
+: 1
push @foo, 'abc' =~ /abc/;      print scalar @foo, "\n";      # output
+: 2
push @foo, 'abc' =~ /abcd/;     print scalar @foo, "\n";      # output
+: 2 - nothing added to @foo?!
push @foo, '';                  print scalar @foo, "\n";      # output
+: 3
push @foo, 0;                   print scalar @foo, "\n";      # output
+: 4
push @foo, undef;               print scalar @foo, "\n";      # output
+: 5


@foo = ();
print "\n";
push @foo, (1);                 print scalar @foo, "\n";      # output
+: 1
push @foo, ('abc' =~ /abc/);    print scalar @foo, "\n";      # output
+: 2
push @foo, ('abc' =~ /abcd/);   print scalar @foo, "\n";      # output
+: 2 - nothing added to @foo?!
push @foo, ('');                print scalar @foo, "\n";      # output
+: 3
push @foo, (0);                 print scalar @foo, "\n";      # output
+: 4
push @foo, (undef);             print scalar @foo, "\n";      # output
+: 5


@foo = ();
my $bar;
print "\n";
$bar = 1;                 push @foo, $bar;  print scalar @foo, "\n";  
+  # output: 1
$bar = 'abc' =~ /abc/;    push @foo, $bar;  print scalar @foo, "\n";  
+  # output: 2
$bar = 'abc' =~ /abcd/;   push @foo, $bar;  print scalar @foo, "\n";  
+  # output: 3 - this time its been added to @foo
$bar = '';                push @foo, $bar;  print scalar @foo, "\n";  
+  # output: 4
$bar = 0;                 push @foo, $bar;  print scalar @foo, "\n";  
+  # output: 5
$bar = undef;             push @foo, $bar;  print scalar @foo, "\n";  
+  # output: 6
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