Look how interesting:

$ perl -MData::Dumper -e 'print Dumper (do { 1 if $_ }) for undef, 0, 
+"0", ""'
$VAR1 = undef;
$VAR1 = 0;
$VAR1 = '0';
$VAR1 = '';
$ perl -MData::Dumper -e 'print Dumper ($_ and 1) for undef, 0, "0", "
+"'
$VAR1 = undef;
$VAR1 = 0;
$VAR1 = '0';
$VAR1 = '';
$ perl -MO=Concise -e 'sub a { 1 if $_ } print a for undef, 0, "0", ""
+'
k  <@> leave[1 ref] vKP/REFC ->(end)
1     <0> enter ->2
2     <;> nextstate(main 2 -e:1) v:{ ->3
3     <;> nextstate(main 2 -e:1) v:{ ->4
j     <2> leaveloop vK/2 ->k
a        <{> enteriter(next->g last->j redo->b) lK/8 ->h
-           <0> ex-pushmark s ->4
-           <1> ex-list lKM ->9
4              <0> pushmark sM ->5
5              <0> undef s ->6
6              <$> const[IV 0] sM ->7
7              <$> const[PV "0"] sM ->8
8              <$> const[PV ""] sM ->9
9           <#> gv[*_] s ->a
-        <1> null vK/1 ->j
i           <|> and(other->b) vK/1 ->j
h              <0> iter s ->i
-              <@> lineseq vK ->-
f                 <@> print vK ->g
b                    <0> pushmark s ->c
e                    <1> entersub[t2] lKS/TARG,1 ->f
-                       <1> ex-list lK ->e
c                          <0> pushmark s ->d
-                          <1> ex-rv2cv sK/128 ->-
d                             <#> gv[*a] s ->e
g                 <0> unstack v ->h
-e syntax OK
$ perl -MO=Concise -e 'sub a { $_ and 1 } print a for undef, 0, "0", "
+"'
k  <@> leave[1 ref] vKP/REFC ->(end)
1     <0> enter ->2
2     <;> nextstate(main 2 -e:1) v:{ ->3
3     <;> nextstate(main 2 -e:1) v:{ ->4
j     <2> leaveloop vK/2 ->k
a        <{> enteriter(next->g last->j redo->b) lK/8 ->h
-           <0> ex-pushmark s ->4
-           <1> ex-list lKM ->9
4              <0> pushmark sM ->5
5              <0> undef s ->6
6              <$> const[IV 0] sM ->7
7              <$> const[PV "0"] sM ->8
8              <$> const[PV ""] sM ->9
9           <#> gv[*_] s ->a
-        <1> null vK/1 ->j
i           <|> and(other->b) vK/1 ->j
h              <0> iter s ->i
-              <@> lineseq vK ->-
f                 <@> print vK ->g
b                    <0> pushmark s ->c
e                    <1> entersub[t2] lKS/TARG,1 ->f
-                       <1> ex-list lK ->e
c                          <0> pushmark s ->d
-                          <1> ex-rv2cv sK/128 ->-
d                             <#> gv[*a] s ->e
g                 <0> unstack v ->h
-e syntax OK
[download]

Conclusion: $_ and 1 and 1 if $_ is exactly the same thing. perl compiles it to the same bytecode.

---

---

Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!

Titles consisting of a single word are discouraged, and in most cases are disallowed outright.

Read Where should I post X? if you're not absolutely sure you're posting in the right place.

Please read these before you post! —

• How do I compose an effective node title?
• How do I post a question effectively?
• Markup in the Monastery

Posts may use any of the Perl Monks Approved HTML tags:

a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr

You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)

	For:		Use:
	&		&
	<		&lt;
	>		&gt;
	[		&#91;
	]		&#93;

Link using PerlMonks shortcuts! What shortcuts can I use for linking?

See Writeup Formatting Tips and other pages linked from there for more info.