Use regular expressions to add commas to every 3 digits

Summing up the method of adding commas to the numbers, consider the general situation. Provide ideas for everyone to refer to the following

#!/usr/bin/perl UseStrict; Usewarnings;my $num=1234556789;#Pure Data Mode$num=~ s/(? <=\d) (? = (\d{3})+$)/,/G;Print $num,"\ n";#with decimal point mode$num=123456.1234;$num=~ s/(? <!\.\d) (? <=\d) (? = (\d{3}) +\b)/,/G;Print $num,"\ n";#after more than 5 bits ... #\k mode, variable-length negation backward view, \k allow the pattern before it to match but not be replaced. The Replace operation is valid only for the string part after \k. $num=123456.12345;$num=~ s/(? <!\.) (?:\ B|\G) \d+?\k (? = (\d{3}) +\b)/,/G;Print $num,"\ n";

OUTPUT: 1,234,556,789 123,456.1234 123,456.12345

Use regular expressions to add commas to every 3 digits