To a find a year in a string using Regular expression in perl -

input.txt

ken, robert. (1994). lessons hull house contemporary urban university 2008. social service review, 68(3), 299-321.  robert, john. 1994. lessons hull house contemporary urban university 2008. social service review. 

output.txt

ken, robert. (<y>1994</y>). lessons hull house contemporary urban university 2008. social service review, 68(3), 299-321.  robert, john. <y>1994</y>. lessons hull house contemporary urban university 2008. social service review. 

i have tried following coding, tag last occyears can fine me solution

print "enter exp file name without extension: "; chomp($filename = <stdin>); open(red, "$filename.txt") || die "could not open exp file"; open(writ, ">$filename.html");  while(<red>) {     if(/(.+)(\d{4})/) {         s/(.+)(\d{4})/$1<y>$2<\/y>/g;     } print writ $_; } close(red); close(writ); 

you have greedy regex, last year in every line gets matched. ? makes + quantifier non-greedy (don't match as possible)

if (/(.+?)(\d{4})/) {    s/(.+?)(\d{4})/$1<y>$2<\/y>/g; } 

as side note, can simplify above code with

s/(\d{4})/<y>$1<\/y>/g;