I remember the table -- but bdf's comment in Mastering Perl was that 'qr' forms "Regular Expresssion". It's an object of class Regexp and type REGEXP: 
 perl -we'use strict;use P; use Types::Core qw(typ);
my $re = qr{ab};
P "re(=%s), has ref %s, and type %s", $re, ref $re, typ $re;
'
re(=(?^:ab)), has ref Regexp, and type REGEXP

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'perlop' says (*emphasis mine*): 
Binary "=~" binds a *scalar expression* to a *pattern match*.

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Going by: 
perl -we'use strict;use P; 
my $str="part";
my @match_m  = $str =~ m{^(.).*?(.)};
my @match_qr = $str =~ qr{^(.).*?(.)};
sub p_Ar($) { P "#=%d, content=(%s)", scalar(@{$_[0]}), $_[0]};       
+    
P "res1:%s\nres2:%s", p_Ar \@match_m, p_Ar \@match_qr;
'     
res1:#=2, content=(['p', 'a'])
res2:#=2, content=(['p', 'a'])

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It must be the case that both m{} and qr{} are *both* pattern matches. Isn't a "pattern match" a "regular expression pattern"?

The fact that the =~ treats them the same, but the 'g' flag only works on one of them seems counter-intuitive. I realize that "behind the scenes", documentation says they "don't", but why, might not, the 'g' flag apply to sub-pattern, so, at least, things like "\G" would work inside "qr"? (Note, \G is is defined as a legal zero width assertion that appears "usable" in a "qr" pattern (but I'm not sure to what effect w/o "(?g)).

After more than a bit of experimenting, I found '\G' is usable, but a bit awkward to use inside 'qr' op, since it only will work when wrapped with an 'm{}', though even there, for some reason, it returns an extra pair of matches that contain undef: 

> perl -we'use strict; use P qw(:undef="(undef)");
my $qr_string = q((?:\G(\w)\W{2}(\w))*);
my $qr  = qr[$qr_string];

my $base_pat=q(p--t);
sub p_Ar($) { P "#=%d, content=(%s)", scalar(@{$_[0]}), $_[0]};

our (@match_mstr , @match_mqr , @match_qr , @match_qr2 , @tst_names);
@tst_names   = (qw(mstr mqr qr qr2));
local * p_matches; *p_matches = sub ($) { 
    no strict "refs";
    $_ = $base_pat x $_[0];
    @match_mstr  = $_ =~ m{$qr_string}g;
    @match_mqr   = $_ =~ m{$qr}g;
    @match_qr    = $_ =~ $qr;
    @match_qr2   = $_ =~ qr{$qr};
    P qq(For str="%s:\n).(qq(%10s:%s\n) x @tst_names), $_ , 
      (map { ("res_".$_, p_Ar(\@{"match_".$_})) } @tst_names);
    0;
  };
my $c=1;
while (3>=$c) { p_matches($c++) }
'
For str="p--t:
  res_mstr:#=4, content=(['p', 't', (undef), (undef)])
   res_mqr:#=4, content=(['p', 't', (undef), (undef)])
    res_qr:#=2, content=(['p', 't'])
   res_qr2:#=2, content=(['p', 't'])
For str="p--tp--t:
  res_mstr:#=6, content=(['p', 't', 'p', 't', (undef), (undef)])
   res_mqr:#=6, content=(['p', 't', 'p', 't', (undef), (undef)])
    res_qr:#=2, content=(['p', 't'])
   res_qr2:#=2, content=(['p', 't'])
For str="p--tp--tp--t:
  res_mstr:#=8, content=(['p', 't', 'p', 't', 'p', 't', (undef), (unde
+f)])
   res_mqr:#=8, content=(['p', 't', 'p', 't', 'p', 't', (undef), (unde
+f)])
    res_qr:#=2, content=(['p', 't'])
   res_qr2:#=2, content=(['p', 't'])

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ARG!!!... I'm getting a headache.

p.s. -- how does one get unicode characters to display in '<code>'?
Those &#8708;'s (∄), above, are ugly (supposed to be symbol for "There does not exist", i.e.: undef. --- which seems to display ok in normal text, but not inside a '<code>' block. *sigh*

UPDATE: removed/replaced version of code that used the default undef (∄) symbol to use "(undef)" instead.

In reply to Re^2: 'g' flag w/'qr' by perl-diddler
in thread 'g' flag w/'qr' by perl-diddler

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