Re^2: Adding 2 + 2 (digit-less 1)

[ikegami]

That's really an interesting way of getting 1, not 2. Other interesting ways to get 1:

my $one = !@!;
my $one = !!$];
my $one = /.*/;                # Side-effect: Changes $1, etc
my $one = $$/$$;
my $one = ()=$$;
my $one = @{[$$]};
my $one = 'a'^'P';             # Character set specific.
my $one = ord('b')-ord('a');   # Character set specific.

And 2:

my $two = $one+$one;
my $two = $one<<$one;
my $two = ()=qw(a a);
my $two = @{[ qw(a a) ]};
my $two = ()=/(.*)(.*)/;       # Side-effect: Changes $1, etc
my $two = 'a'^'S';             # Character set specific.
my $two = ord('c')-ord('a');   # Character set specific.

None of these have side effects unless otherwise noted.
All of these run under use strict;.
All of these run silently under use warnings;.

[ambrus]

There's also length $=.

I also have a table for all numbers: Re: Re: exactly 390 bytes. It says log hex c.

[vrk]

More (although not as neat):

my $one = !$|;
my $one = cos;        # Given that $_ == 0.
my $one = cos $|;
my $one = cos atan2 $|, cos;
my $one = sin atan2 sin, $|;
my $one = length $/;  # Note: possibly 2 under Windows or DOS. 
my $one = length $";
my $one = length $;;
my $one = length $^L;
my $one = $^T/$^T;
my $one = @ARGV >= 0;
my $one = grep //, ($_);
my $one = !undef;
# Note: the following may be Unix-only. Will not work if run as root,
# as root's UID and GID are (always?) zero.
my $one = $</$<;      # User ID.
my $one = $>/$>;      # Effective user ID.
my $one = $(/$(;      # (Space-separated list of) group ID(s).
my $one = $)/$);      # (Space-separated list of) effective group ID(s
+).

Ways to get 2:

my $two = length $:;
my $two = $^F;        # Note: system-dependent.