Assuming the file already exists, yes append mode would be better. If it doesn't already exist, then the two are equivalent. To make it more similar to touch it should be appending. You're right about that.

At least in my environment (AIX), opening the file in append mode without adding any content does not update the modification date of the file.

$: date
Thu Jan  7 09:37:01 CST 2016
$: touch step.file
$: ls -l step.file
-rw-r--r--    1 wlsedi   wlsedi            0 Jan 07 09:37 step.file
$: date
Thu Jan  7 09:38:01 CST 2016
$: touch step.file
$: ls -l step.file
-rw-r--r--    1 wlsedi   wlsedi            0 Jan 07 09:38 step.file
$:  date
Thu Jan  7 09:39:38 CST 2016
$: perl -de 1

Loading DB routines from perl5db.pl version 1.28
Editor support available.

Enter h or `h h' for help, or `man perldebug' for more help.

main::(-e:1):   1
DB<1> open $fh,'>>','step.file'
DB<2> close $fh
DB<3> q
$: ls -l step.file
-rw-r--r--    1 wlsedi   wlsedi            0 Jan 07 09:38 step.file
[download]

Opening in write does have the un-touchlike side effect of wiping out any content. In this particular instance, that is of no consequence, but using the code as a generic replacement for touch is problematic.

File::Touch if you want a generic replacement.