PERL + match exactly string(from left side) in line

Question

Hi all

I have problem with the following perl command How to match all "1234" strings in file, but if some characters jointed before "1234" then it will not match, my problem is: if the string "1234" in the middle of the line then it not match why?

The perl command:

perl  -pe 's/OLD/NEW/ if /^1234/' file

Example of what need to match:

a ass 1234= OLD
bbb ddd 1234= OLD
 1234= OLD

Example of what not need to match:

a1234=  OLD
sss q1234=  OLD

Answer 1

The ^ matches "the beginning of the line". Try removing that character in the regular expression. Replace it with a space character.

Answer 2

Change the ^ to \b. That will match only if the 1234 is the start of a word. (If necessary, see perldoc perlre for more information on what constitutes a 'word'!)