Or, for a less verbose version that doesn't require taint mode, 5.10, or a shouty license (consider it public domain): 
use Fcntl ':mode';

my %TYPE = (S_IFDIR,'d',S_IFCHR,'c',S_IFBLK,'b',S_IFREG,'-',S_IFLNK,'l
+',
            S_IFSOCK,'s');

sub o
{
    my ($mode, $xr, $xid) = @_;
    (($mode & ($xr | $xid)) == ($xr | $xid)) ? 's'
        : ($mode & $xr) ? 'x' : ($mode & $xid) ? 'S' : '-';
}

sub strmode
{
    my ($mode) = @_;
    ($TYPE{$mode & S_IFMT} || '?')
        . (($mode & S_IRUSR) ? 'r' : '-')
        . (($mode & S_IWUSR) ? 'w' : '-')
        . o($mode, S_IXUSR, S_ISUID)
        . (($mode & S_IRGRP) ? 'r' : '-')
        . (($mode & S_IWGRP) ? 'w' : '-')
        . o($mode, S_IXGRP, S_ISGID)
        . (($mode & S_IROTH) ? 'r' : '-')
        . (($mode & S_IWOTH) ? 'w' : '-')
        . o($mode, S_IXOTH, S_ISVTX)
}

[download]
EDIT: Actually, this problem makes a decent golf hole. Given some files in @ARGV, print "modestring file\n" for each file. Here's a start (283 262 222 203 strokes w/o newlines): 
#!/usr/bin/perl -l
sub i{'-'}
sub o{$m&$_[0]?$m&$_[1]?'s':x:$m&$_[1]?S:i}
print qw(? c d b - l s)[($m=(lstat)[2])>>13]
,$m&256?r:i
,$m&128?w:i
,o(64,2048)
,$m&32?r:i
,$m&16?w:i
,o(8,1024)
,$m&4?r:i
,$m&2?w:i
,o(1,512)
," $_"for@ARGV;

[download]
EDIT: Or, with bitwise goodness, 131 127: 
#!/usr/bin/perl -l
for$f(@ARGV){
$_=sprintf"%9b",($m=(lstat$f)[2])&511;
y/01/\0\xff/;
$_&=rwxrwxrwx;
y/\0/-/;
print qw(? c d b - l s)[$m>>13],"$_ $f"
}

[download]

In reply to Re: strmode in Perl (convert octal permissions to symbolic) by educated_foo
in thread strmode in Perl (convert octal permissions to symbolic) by afresh1

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