Why would this be a problem?

You can replace $f[4] with with int($f[4]) . " " x (length $f[4] - length int($f[4]));

Or you could use a regex instead of split...

Regex you could use:

Compact form:
s/(\d+(?:\.\d+)?)(?=(?:\s+\S+){4}$)/int ($1) . " " x (length($1) - length(int($1)))/eg;

Long way: 

    s/
     (         # Capture group $1
       \d+     # Digits
       (?:     # Group (no capturing) (optional group)
         \.    # a dot
         \d+   # Digits
       )?
     )         # End capture $1

     (?=       # Open look-ahead
       (?:     # Group (no capturing)
         \s+   # Whitespace
         \S+   # Non-whitespace
       ) 
       {4}    # Match previous group exactly four times
       $      # Match end of line
     )
    /int ($1) . " " x (length($1) - length(int($1)))/egx;

[download]

Note: small version tested, big version untested

Update: forgot length, added a possible regex

In reply to Re: changing a portion of a line leaving its formatting intact by Animator
in thread changing a portion of a line leaving its formatting intact by bronto

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