Here's the data on 2 animations with similar filesize, parts (frames), colortable, and delay but I still can't see why the slow one spends so much time in Tk::image::new:

 my $obj = $widget->Tk::image('create',$leaf,@_); # the slowest line of code

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GIF1 3.9M
66 parts
Tk::Animation took 3.60994100570679 seconds for 4096259 bytes

Stmts	Exclusive
	Time 		Source File
490	3.29s	line	Tk/Image.pm
659	812ms	line	Tk.pm
102086	274ms	line	Image/Info/GIF.pm

# spent 3.29s (2.17ms+3.29) within Tk::Image::new which was called 68 times, avg 48.4ms/call: 
# 67 times (2.15ms+3.29s) by Tk::Animation::new at line 37 of Tk/Animation.pm, avg 49.1ms/call 
# once (28µs+2.33ms) by Tk::Animation::new at line 26 of Tk/Animation.pm

# spent 121ms (57.5+63.4) within Image::Info::GIF::my_read which was called 16632 times, avg 7µs/call:
# 16094 times (56.0ms+63.3ms) by Image::Info::GIF::seek_data_blocks at line 50, avg 7µs/call
#   203 times (582µs+47µs) by Image::Info::GIF::read_data_blocks at line 41, avg 3µs/call
#   134 times (375µs+50µs) by Image::Info::GIF::process_file at line 110, avg 3µs/call
#    67 times (166µs+13µs) by Image::Info::GIF::process_file at line 152, avg 3µs/call
#    66 times (179µs+20µs) by Image::Info::GIF::process_file at line 143, avg 3µs/call
#    66 times (164µs+10µs) by Image::Info::GIF::process_file at line 126, avg 3µs/call
#        once (11µs+9µs) by Image::Info::GIF::process_file at line 59
#        once (1µs+1µs) by Image::Info::GIF::process_file at line 99

BackgroundColor  0
ColorResolution  8
ColorTableSize 	 256
Delay 	         0.08
DisposalMethod 	 1
GIF_Loop 	 forever
GIF_Version 	 89a
GlobalColorTableFlag 	 1
ScreenHeight 	 360
ScreenWidth 	 300
SortedColors 	 0
XPosition 	 0
YPosition 	 0
color_type 	 Indexed-RGB
file_ext 	 gif
file_media_type  image/gif
height 	         360
resolution 	 1/1
width 	         300

---

GIF2 4.9M
60 parts
Tk::Animation took 33.700756072998 seconds for 5088374 bytes 

Stmts	Exclusive
	Time 		Source File
448	33.4s	line	Tk/Image.pm
645	738ms	line	Tk.pm
124973	254ms	line	Image/Info/GIF.pm
	
# spent 33.4s (1.58ms+33.4) within Tk::Image::new which was called 62 times, avg 539ms/call:
# 61 times (1.54ms+33.4s) by Tk::Animation::new at line 37 of Tk/Animation.pm, avg 548ms/call
#     once (39µs+6.58ms) by Tk::Animation::new at line 26 of Tk/Animation.pm

# spent 112ms (54.6+57.9) within Image::Info::GIF::my_read which was called 20478 times, avg 5µs/call:
# 19957 times (53.3ms+57.7ms) by Image::Info::GIF::seek_data_blocks at line 50, avg 6µs/call
#   214 times (539µs+57µs) by Image::Info::GIF::read_data_blocks at line 41, avg 3µs/call
#   123 times (284µs+40µs) by Image::Info::GIF::process_file at line 110, avg 3µs/call
#    62 times (117µs+14µs) by Image::Info::GIF::process_file at line 152, avg 2µs/call
#    60 times (167µs+6µs) by Image::Info::GIF::process_file at line 126, avg 3µs/call
#    60 times (130µs+15µs) by Image::Info::GIF::process_file at line 143, avg 2µs/call
#        once (16µs+16µs) by Image::Info::GIF::process_file at line 59
#        once (5µs+2µs) by Image::Info::GIF::process_file at line 99

BackgroundColor.  0
ColorResolution   8
ColorTableSize 	  256
Delay 	          0.03
DisposalMethod 	  1
GIF_Loop 	  forever
GIF_Version 	  89a
GlobalColorTableFlag 	 1
ScreenHeight 	  480
ScreenWidth 	  480
SortedColors 	  0
TransparencyIndex 255
XPosition 	  0
YPosition 	  0
color_type 	  Indexed-RGB
file_ext 	  gif
file_media_type   image/gif
height 	          480
resolution 	  1/1
width 	          480

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Thank you