Multiply all numbers in a string Winner: Chilemagic, a massive 21 bytes!
You may continue to submit your answer, however you can no longer win. Original post kept:

Your goal is to find all numbers in a string, and multiply each one individually by a value input by the user

You will not need to worry about decimals
The user will input a number and a string
The user must type the number and string at some point, however the method the program reads it does not matter. It can be with stdin, reading a text file, etc, however the user must press the 9 button on their keyboard (for example) at some point
Anything that can compile and run is acceptable

Example:
Sentence input: This 1 is22a 3352sentence 50
Number input: 3
Output: This 3 is66a 10056sentence 150


This contest ends on September 6th, 2014 (7 days from posting).
This is a code-golf, so the shortest code wins
Update - Perl - 17

s/\d+/$&amp;*$^I/ge


15 characters + 2 for -i and -p flags.

We can use the -i flag to input a file extension, but since we aren't reading any files, we can use it to get the number and it the variable $^I will get assigned to it.

Run with:

perl -e'print"This 1 is22a 3352sentence 50"' | perl -i3 -pe's/\d+/$&amp;*$^I/ge'


Perl - 21

Updated as per @Dennis's comment.

$n=&lt;&gt;;s/\d+/$&amp;*$n/ge


Run with -p flag.

Example run:

perl -e'print"This 1 is22a 3352sentence 50\n3"' | perl -pe'$n=&lt;&gt;;s/\d+/$&amp;*$n/ge'


Explanation:

$n=&lt;&gt;; read in the number

-p prints the output

s/\d+/$&amp;*$n/ge Read the input with &lt;> and search for one or more digits and replace them with the digits times the number. g is global, e is eval the replace potion of the s///. $&amp; contains what was matched and it multiplied by the number, $n.

You can read more about s/// in perlop and more about Perl regexes in perlre.

Another solution:

@F.Hauri pointed out you can also use the s switch to assign the $n variable to 4. I'm not sure how many characters this counts as but I'll leave it here:

perl -spe 's/\d+/$&amp;*$n/ge' -- -n=4 &lt;&lt;&lt;'This 1 is22a 3352sentence 50'