The  s/// substitution  /r modifier is only available from Perl version 5.14 onwards. kennethk has shown how to use the  /r modifier, but if you have a Perl version prior to 5.14 and wish to preserve the original string, use method B below: 

c:\@Work\Perl>perl -wMstrict -le
"my $adate = '2017-01-29 11:30:07.370';
 ;;
 my $A_new = $adate =~ s/(\d{4})-(\d{2})-(\d{2})\s(\d{2}):(\d{2})(.*)/
+$2-$3-$1 $4:$5/r;
 print qq{A: new '$A_new'  old '$adate'};
 ;;
 (my $B_new = $adate) =~ s/(\d{4})-(\d{2})-(\d{2})\s(\d{2}):(\d{2})(.*
+)/$2-$3-$1 $4:$5/;
 print qq{B: new '$B_new'  old '$adate'};
"
A: new '01-29-2017 11:30'  old '2017-01-29 11:30:07.370'
B: new '01-29-2017 11:30'  old '2017-01-29 11:30:07.370'

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In both cases, the original string, $adate in this case, is left unchanged. If you do not mind changing this variable, just use a normal  $string =~ s/// substitution.

Give a man a fish:  <%-{-{-{-<

In reply to Re: Assigning a parsed date to a variable by AnomalousMonk
in thread Assigning a parsed date to a variable by Anonymous Monk

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