Doing a loop to change a value in a file

Hi, I have an N number of files in a directory. I like to write a shell script that would make identical plots for each one of these files.

The files have names such as:

t00001.dat
t00002.dat  
t00003.dat  
t00004.dat  
t00005.dat
       .
       .
       .
t00040.dat

i.e. the filename is incrementing numerically from a value of 1 to N.

I plot some variables from these files using gnuplot. So in my gnuplot plotting script (plot.gplt) I have the following line which plots the function:

plot 't00001.dat' using 1:2

I know that using a perl script I could change the filename 't00001.dat' incrementally. But with my limited knowledge in shell scripting I don't know how to do this.

Thanks!

How about:-

printf "%s\n" t*.dat | sort | while read file
do
   plot '"$file"' using 1:2
done

for file in t*.dat
do
  plot "'$file'" ...
done

for i in {1..40}; 
do 
 str=$(printf %05d $i)
 plot \'"t$str.dat"\' using 1:2
done

Thanks for the replies. I'm sorry I didn't explain my problem clearly.

I have a gnuplot script file that does the plotting (called time.gplt), in it I have the following line that plots the data.

plot 't00001.dat' using 1:2

Using rdcwayx's method I've been able to do most of what I want, i.e:

for i in {1..40};
do
        str=$(printf %05d $i)
        perl -i -pe "/plot/&&s/t\d+/t$str/" time.gplt
        gnuplot time.gplt
done

But now I have the following questions

1) is it possible to use something like

n=$(ls -l t?????.dat | wc -l)

to calculate the number of files and then use that to define the number of loops?

2) Also I have the following line in my gnuplot script (time.gplt) which I would like to modify:

set label at 14,10 '$t=1.0$~ms'

I would like to replace the number after the equal sign in the above code with the variable $str?

Thanks!