Sample Code for searching for several sub-characters (strings) in Perl

1) how to find the number of times a character appears in a string?
Source: http://www.perl.com/doc/FAQs/FAQ/oldfaq-html/Q4.24.html
If you want to find the number of occurrences of a character (x) in a string, you can use the tr // function and use the following methods to implement it:
$ String = "thisxlinexhasxsomexx 'sxinxit": $ COUNT = ($ string = ~ TR/X //); print "There are $ count Xs in the string ";
2) how to find the number of times a substring appears in a string?
The above CodeIt is very effective for you to only search for a single character. However, if you try to calculate a substring consisting of multiple characters and the number of occurrences in a large string, the function tr // does not work. At this time, we need to add a while loop:
$ String = "-9 55 48-2 23-76 4 14-44"; $ count ++ while $ string = ~ /-\ D +/g; print "There are $ count negative numbers in the string ";
3) query the number of lines in a string in a file in Perl and the contents of the lines containing the string.
Source: http://www.perlmonks.org /? Node_id = 650671
We can use the following code to implement the sub-process retriver () for reading files and searching.
Use strict; Use warnings; sub retriver (); my @ lines; my $ lines_ref; my $ count; $ lines_ref = & retriver (); @ lines = @ $ lines_ref; $ COUNT = @ lines; print "count: $ count \ nlines \ n"; print join "\ n", @ lines; sub retriver () {my [...]