Please stop using my mail address when replying, I'm on the list and
don't want two copies of the same mail (it's not about you Mike).
Mike <te...@mflan.com>
> Why is my Perl not working on that command?
>
> $ perl -e 'exit(10) if "aaa"=~/a{,2}/;'
> Unescaped left brace in regex is illegal here in regex; marked by <--
> HERE in m/a{ <-- HERE ,2}/ at -e line 1.
> $
>
> But this works:
> $ perl -e 'exit(10) if "aaa"=~/a{0,2}/;'
> $
>
> $ echo $?
> 10
> $
On an old debian woody box I get:
$ perl -v | grep v5
This is perl, v5.6.1 built for i386-linux
$ perl -e 'exit(10) if "aaa"=~/a{,2}/;'; echo $?
0
$ perl -e 'exit(10) if "aaa"=~/a{0,2}/;'; echo $?
10
$ man perlre
...
The following standard quantifiers are recognized:
* Match 0 or more times
+ Match 1 or more times
? Match 1 or 0 times
{n} Match exactly n times
{n,} Match at least n times
{n,m} Match at least n but not more than m times
...
So, old perl versions don't have the {,m} quantifier, check your
documentation for that. The easy way out is to always use {0,m} instead
of {,m}, which is the same thing in modern perl, actually there is no
need ever to use the {,m} quantifier.
I don't know why I don't get a perl error message above, maybe a bug.
///
On a more uptodate system I get:
$ perl -v | grep v5
This is perl 5, version 34, subversion 1 (v5.34.1) built for
x86_64-linux-thread-multi
$ perl -e 'exit(10) if "aaa"=~/a{,2}/;'; echo $?
10
$ perl -e 'exit(10) if "aaa"=~/a{0,2}/;'; echo $?
10
///
If you are interested of the syntax rules, check under "Simple
statements" in:
(perl 5.6.1)
$ man perlsyn
Any simple statement may optionally be followed by a SIN-
GLE modifier, just before the terminating semicolon (or
block ending). The possible modifiers are:
if EXPR
unless EXPR
while EXPR
until EXPR
foreach EXPR
...
(perl 5.34.1)
$ man perlsyn
...
Statement Modifiers
Any simple statement may optionally be followed by a SINGLE modifier,
just before the terminating semicolon (or block ending). The possible
modifiers are:
if EXPR
unless EXPR
while EXPR
until EXPR
for LIST
foreach LIST
when EXPR
...
So, modern perl also have "for" and "when".
///
Also note that in a compound statement you have to ()'ize the EXPR as in
if (EXPR) BLOCK elsif (EXPR) BLOCK ... else BLOCK
in contrast to for the modifier you don't need to:
STATEMENT if EXPR;
I prefer to always to use ()' around the expression, since it makes it
easier to convert between the two forms.
Regards,
/Karl Hammar
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