[perl #68600] Tainting $! breaks the string part of its magic in 5.8.9 and later

# New Ticket Created by  David Taylor 
# Please include the string:  [perl #68600]
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# <URL: http://rt.perl.org/rt3/Ticket/Display.html?id=68600 >


If a tainted value is assigned to $!, subsequent $! reads return the
numeric errno in both string and number contexts, until the taint
magic is removed from $! by assigning something untainted to it.

# without -T
$ perl -e '$! = substr("0".join("", %ENV), 0, 1); open my $f, "<",
"..."; print "$!\n"'
No such file or directory

# same thing with -T
$ perl -Te '$! = substr("0".join("", %ENV), 0, 1); open my $f, "<",
"..."; print "$!\n"'
2

Observed in Perls 5.8.9, 5.10.0, 5.10.1-RC1.  5.8.8 and earlier are
not effected.

• [perl #68600] Tainting $! breaks the string part of its magic in 5.8.9 and later by David Taylor